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Old 12-08-2012, 09:43 PM
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Toobuilder Toobuilder is offline
Join Date: Jul 2009
Location: Mojave
Posts: 4,928
Thumbs up Hot #3 CHT - Solved!

So in the course of changing out my injector lines, I decided to attack my #3 cylinder temperature issue. This cylinder has always been my "problem child" on climb and also in cruise. It typically runs hotter than my coolest cylinder (#4) by a wide margin (usually about 70 - 80 degrees in the summer) in cruise. Always. Anyway, I decided to deconstruct the rear baffle and see what I could do to direct some air through the fins. Then it struck me... With the Vans supplied baffles, there is no way air can get from the top of the cylinder to the bottom on the intake side of the head because the fins terminate at the equator of the cylinder. The wrap around baffle on the bottom has essentially no supply of air. So not only is there no airflow around the bottom, the top fins are simply radiating heat into stagnant air. So I figured we needed to get some air moving past the top and bottom fins to see if the temps would come down. I fabricated a plenum to get the air moving in an organized fashion and attached it to the existing baffle.

Long story short, I finished it up this afternoon and was blessed with good flying weather. I decided to climb to my normal cruise altitude of 7500 feet to see if the mod did anything. I tried an agressive climb to stress the cooling and was greeted with the typical #3 cylinder behavior of leading the numbers. Great! All that work for no gain. But as I pushed over into cruise, the temps started to fall. And wouldn't you know it, the problem child kept falling - eventually stabilizing at a temp only a few degrees warmer than my coolest. So this one fairly simple mod brought my hottest cylinder all the way down to the second from coldest. Now my hottest is #2 - which also features the same airflow blockage by virtue of the Vans baffles. Time to work on that one and get it into line with the others.

WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
Harmon Rocket II -SDS EFI
1940 Taylorcraft BL-65
1984 L39C - SOLD

Last edited by Toobuilder : 12-09-2012 at 09:32 AM.
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